The present invention relates to implants, and more particularly to an inflatable implant including separate inner and outer lumens and an improved valve and filling tube construction. The present invention finds particular use in implants used in breast reconstruction and augmentation.
Breast reconstruction often is difficult after a mastectomy because of tight chest wall skin and scarring. It is desirable to expand the skin which allows the surgeon to avoid using skin from other parts of the body. To this end, temporary skin expanders have been used in breast reconstruction, and these are then replaced with a suitably sized, permanent implant. It will be appreciated that this requires two or more surgical procedures.
There are many permanent implants on the market which are useful in breast reconstruction and augmentation. The most commonly used is a single lumen, fixed volume implant utilizing silicone gel. The major drawback in this implant arises from gel bleed which causes capsular contracture. The major advantage is the natural feel which is extremely good.
In an attempt to overcome the "bleed" problem, saline filled implants have been developed. These have greatly reduced the capsule contracture problem, but the feel is not as good. Also, the saline filled implants are subject to spontaneous leakage caused by wave-like motion of the saline which is transmitted to the implant membrane.
There are various "combination" implants, some using a double lumen construction with gel in the inner chamber and saline in the outer chamber, and some with a polyurethane sponge coating to decrease capsule contracture.
A very important goal in implants of this nature is to achieve a natural feel and appearance and to minimize leakage and capsular contracture. Another goal is to facilitate expansion after implantation and to permit volume adjustment.
One implant currently available is that marketed by Cox-Uphoff International termed a Reverse Double Lumen Mammary (RDL.sub.TM). This is a double membrane, double lumen construction having an outer membrane containing a gel and an inner membrane which is filled with saline. The inner and outer membranes are connected at a retention valve which allows insertion of a rigid filling tube from outside the implant into the inner lumen. By this construction, saline can be injected into the inner lumen at the time of implantation to fill the implant. Upon completion of the filling process and before skin closure, the filling tube is removed. For an explanation and understanding of the retention valve construction described here, reference may be made to U. S. Pat. No. 4,178,643.
The double lumen construction of the CUI implant utilizing silicone gel in the outer lumen and saline in the inner provides a very natural and high quality appearance and feel. However, shear forces arise in this implant at the connected area of the membranes which increases the incidence of leakage. Also, the connected membranes inhibit free movement of the inner and outer membranes relative to each other and detracts from the natural feel and appearance of the implant.
In addition, the filling tube and filling valve constructions in those prior implants which can be filled at the time of surgery are not suitable for inflation or volume adjustment after implantation. A rigid filling tube is required and cannot be left in place for any long period of time because of the danger of puncturing the implant and because of discomfort to the patient caused by the rigid tube. Thus, these implants cannot function as an expander.
It is important that the implant valves be constructed of a soft and pliable material because the valve is a part of the implant and remains in place with the implant. The filling tubes used with these implants often are in place in the valves for some time (in prior devices, before implantation) so that the soft and pliable valve material can become "set" and not recover its original shape when the tube is removed. Still further, such prior valves and filling tubes do not always sealingly cooperate in the desired fashion when the tube is in place. Thus, a relatively high incidence of leakage can result in these implants acting to the detriment of these devices as permanent implants.